In general terms, this invention relates to elevator speed control. More particularly, this invention relates to a device that is useful for preventing an elevator car from moving beyond a desirable speed.
Elevator control systems typically include a variety of components or devices for controlling movement of the elevator cab within a hoistway. One such device is known as a governor and is often associated with the motor that drives the elevator system components or with at least one of the sheaves that rotates as the elevator cab moves between landings within a building, for example. Typical governors are intended to stop the elevator cab from moving beyond a desired speed in a downward direction.
Centrifugally activated elevator governors that are associated with sheaves are known. One example includes a set of arcuate plates that move from a retracted position into an extended position where they provide a braking capability responsive to the rotary movement of the sheave beyond a desired speed as the elevator cab moves downward. While such centrifugally activated governor devices have been successfully employed for preventing downward movement of an elevator cab, there has not been a corresponding type of governor that is useful for stopping undesirable upward movement of an elevator cab.
While various devices have been proposed or utilized for controlling undesirable upward movement of an elevator cab, they introduce additional complexity and expense into elevator systems. There is a need for a compact, robust device that is readily accommodated within an elevator system to control elevator cab movement in both directions. An assembly designed according to this invention provides that capability and avoids the shortcomings and drawbacks of prior arrangements.